Fuel injection arrangement for internal combustion engines with accelerating enrichment

ABSTRACT

A fuel injection arrangement for enriching the air-fuel mixture during acceleration of the engine. The duration of a pulse applied to the electromagnetically actuated injection valve of the engine, is varied as a function of the pressure prevailing within the intake manifold of the engine. The pulse is supplied by a monostable multivibrator circuit which is actuated synchronously with the rotation of the engine crankshaft. The manifold includes two separate throttles with one throttle positioned by the gas pedal of the engine, and the second throttle positioned through a pressure difference sensing device which measures the difference between the pressure of the intake manifold between the two throttles, and in the intake direction of the manifold. A pressure sensor communicating with the intake manifold between the two throttles varies the inductance of a transformer which operates in conjunction with the monostable multivibrator.

United States Patent [72] Inventor Hermann Scholl Stuttgart, Germany[21] Appl. No. 834,302 [22] Filed June 18,1969 [45] Patented June 1,1971 [73] Assignee Robert Bosch G.m.b.I1.

Stuttgart, Germany [32] Priority June 27, 1968 [33] Germany [31] P 17 51605.1

[54] FUEL INJECTION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES WITHACCELERATING ENRICl-IMENT 10 Claims, 3 Drawing Figs.

[52] U.S. Cl 123/140MP, l23/32AE, 123/119R [51] Int. Cl ..F02m 63/00[50] Field of Search 123/119, 32 E, 32 E-1,l27,139.17,139.l8,140.2,140.3

[56] References Cited UNITED STATES PATENTS ,4 2,896,600 7/1959Scherenberg 123/140.3

2,962,015 11/1960 Serruysetal. 3,463,129 8/1969 Babitzkaetal.

Primary Examiner-Laurence M. Goodridge Att0rney-Michael S. StrikerABSTRACT: A fuel injection arrangement for enriching the air-fuelmixture during acceleration of the engine. The duration of a pulseapplied to the electromagnetically actuated injection valve of theengine, is varied as a function of the pressure prevailing within theintake manifold of the engine. The pulse is supplied by a monostablemultivibrator circuit which is actuated synchronously with the rotationof the engine crankshaft. The manifold includes two separate throttleswith one throttle positioned by the gas pedal of the engine, and thesecond throttle positioned through a pressure difference sensing devicewhich measures the difference between the pressure of the intakemanifold between the two throttles, and in the intake direction of themanifold. A pressure sensor communicating with the intake manifoldbetween the two throttles varies the inductance of a transformer whichoperates in conjunction with the monostable multivibrator.

t if 10 i 11 FUEL INJECTION ARRANGEMENT FOR INTERNAL COMBUSTION ENGINESWITH ACCELERATING ENRICIIMENT BACKGROUND OF THE INVENTION The presentinvention resides in an electrically controlled fuel injectionarrangement adapted for internal combustion engines having at least oneelectromagnetically actuated injection valve. A control arrangementwhich is actuated synchronously with the speed of the engine cooperateswith a pressure-sensing device located behind the throttle member withinthe intake manifold, when viewed from the intake direction. The controlarrangement delivers opening pulses for the injection valve, such thatthe duration of the pulses is dependent upon the pressure prevailingwithin the intake manifold.

In internal combustion engines with fuel injection arrangements forintake manifold injection and remote ignition, a richer mixtureisrequired when the throttle is opened corresponding to initiating andaccelerating process. Thus, during the acceleration interval in goingfrom a lower speed to a higher engine speed, the injected mixturerequires a higher proportion of fuel, than it does in the steady stateoperation in which the throttle position remains constant and theopening angle of the throttle flap thereby also remains constant. Anaccelerating enrichment for electrically controlled fuel injectionarrangements, can be achieved in a relatively simple manner when thequantity of injected fuel is made dependent upon the prevailing throttleposition and the speed of the engine. Since the injected quantity offuel is dependent upon the duration of the opening pulse applied-to theinjection valve, the duration of the individual injection processesduring which the injection valves are opened must thereby be madedependent upon the prevailing throttle position and the rotational speedof the engine. When such a system is used, however, and the duration ofthe individual opening pulses are made dependent upon the suctionpressure within the intake manifold, specific difficulties areencountered. Thus, in such a system the intake manifold pressure risesonly with considerable delay after the opening motion of the throttleflap.

Accordingly, it is an object of the present invention to provide aninjection arrangement of the aforementioned character with a fuelinjection arrangement controlled by the intake manifoldpressure, whichassures that mixture enrichment is realized without fail during thetransient interval when the throttle is opened. The arrangement is suchthat the enrichment takes place prior to the. intake of the added airmass.

In accordance with the present invention, the principle of theaccelerating enrichment arrangement rests upon the provision of a secondthrottle behind the gas pedal actuated throttle, when viewed from theintakedirection. This second throttle is controlled through the pressuredifference prevailing between the pressure behind the first throttle andbehind itself, of the second throttle corresponding to the air suctionpressure. The pressure sensor communicates with the section within theintake manifold which lies between the first and second throttles. Aparticular advantageous design of the present invention results when theopening time constants or the second throttle flap may be freelyselected. Through such a design, it is possible to inject the optimumquantity of fuel with respect to the air mass during the transientinterval, in which the engine is being accelerated.

SUMMARY OF THE INVENTION A fuel injection arrangement for internalcombustion engines. Electromagnetically actuated injection valves haveopening pulses applied to them from a control circuit which consists ofa monostable multivibrator operating in conjunction with a transformer.The inductance of the transformer is made variable as a function of thepressure prevailing within the intake manifold of the engine. Twothrottles are provided within the intake manifold, such that onethrottle is operated by the gas pedal of the engine, whereas the secondthrottle lies behind the first throttle when viewed from the intakedirection of the manifold. The pressure-sensing device which adjusts theinductance of the transformer in the pulse-generating circuit issituated between the two throttles and communicates with the intakemanifold therebetween. The monostable multivibrator is actuated by a camoperated switch, the latter is, in turn, operated synchronously with therotation of the engine crankshaft. A pressure difference sensing deviceincludes a membrane member which is positioned as a function of thedifference between the pressure prevailing within the intake manifoldbetween the two throttles, and the pressure behind the second throttle,with respect to the intake direction of the manifold. This membranewithin the pressure difference sensing device positions the secondthrottle.

The novel features which are considered as characteristics for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a functional schematicdiagram and shows the fuel injection arrangement with the electricalcontrolling circuit, in accordance with the present invention; and

FIG. 2 is a partial sectional view of the intake manifold of the engineof FIG. 1, and shows the throttle-positioning devices of the presentinvention; and

FIG. 3 is a partial sectional view of a modification of the intakemanifold shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, thefuel injection arrangement of FIG. 1 is adapted to a four-cylinderinternal combustion engine 10 used to drive a motor vehicle. The sparkplugs 11 are connected to a high voltage ignition arrangement, notshown. In direct proximity of the inlet valves of the engine, which arenot shown, an electromagnetically actuated injection valve 13 isprovided for each individual cylinder branched off from the intakemanifold 12. Fuel is applied to each injection valve from a distributor15, by way of the fuel lines 14. The fuel is supplied from a storagetank 18 by means of a pump 16 driven through an electric motor. Theintake of the pump 16 drips into the fuel storage tank 18, whereas theoutlet of the pump 16 is applied to a pressure regulator 17. The latteris interposed between the pump 16 and the distributor 15. It is thefunction of the pressure regulator 17 to maintain the fuel pressurewithin the distributor l5 and the fuel lines 14 at substantiallyconstant value of approximately 2 atmospheres. Thus, as a result of thepressure regulator 17, the pressure of the fuel in front of theinjection valves is maintained substantially constant.

Each of the injection valves 13 contains a magnetizing coil, not shown,which has one terminal connected to ground potential. The other terminalof the magnetizing coils is connected to one of the resistors 20, by wayof one of the connections 19. The resistors 20 are coupled together atone of their terminals, and also to the collector of a power transistor21. The base of the power transistor 21 is connected to a transistoramplifier 22 to which square wave or rectangularshaped control pulses 23are applied from an electronic regulating and control circuit to bedescribed further subsequently. The control pulses 23 are generated forevery revolution of the crankshaft 24. The arrangement is such that eachone of the injection valves 13 receives current through its magnetiz ingcoil, for the duration of the pulse 23. For every injection process orcycle, the quantity of fuel injected into the intake manifold and hencefrom there into the cylinder, is proportional to the opening duration ofthe injection valve, which in turn, is proportional to the duration ofthe pulse 23. Such quantity of injected fuel, therefore, must be matchedor fitted to the operating requirement of the internal combustionengine.

The regulating and control circuit 25 which lies within the broken linesin FIG. 1, includes essentially a monostable multivibrator which has afirst switching transistor T, of the PNP type, and a second transistor Tof the same type. The emitters of both transistors are connected to thepositive voltage supply line 26 of a voltage source in the form of thebattery used for the motor vehicle. The nominal voltage of such abattery is 12.6 volts. The collectors of the two transistors T, and Tlead to the negative voltage supply line 29, by way of the resistors 27and 28, respectively. The negative voltage supply line 29 is coupled toground potential.

In the normal or quiescent state of the circuit 25, the transistor T, ismaintained in the conducting state through the resistor 30 which isconnected between its base and the negative voltage supply line 29. Thetransistor T, is thereby turned off. The baseof the transistor T,,furthermore, leads to a capacitor 33. A resistor 34 is connected betweenone electrode of the capacitor and the positive voltage supply line ofthe battery. The other electrode of the capacitor 33 leads to thenegative voltage supply line 29, by way of a resistor 35. The electrodeof the capacitor 33 which is connected to the resistor 35, is alsojoined to a switch 32 operated by a cam 31 which is rotated inaccordance with the crankshaft 24 of the engine 10. When the switch 32is in the open circuit position, the capacitor 33 becomes charged sothat negative potential appears at the electrode connected to theresistor 35 and switch 32. When the switch 32 becomes actuated to closedcircuit position by the cam 31, on the other hand, this negativelycharged electrode of the capacitor 33 becomes connected to the positivevoltage supply line 26. Thus, the unstable state of the monostablemultivibrator circuit becomes initiated when the switch 32 is actuatedto closed circuit position. During this unstable state of the monostablemultivibrator, the opening duration of the magnetic valves 13 isestablished. Once the unstable state of the monostable multivibrator hasbeen initiated, the transistor T, is turned off, and the transistor T,together with the power transistor 21 become conducting, and as a resultthe magnetic valves 13 become opened. The magnetic valves become againclosed when the transistors T, and T, of the monostable multivibratorcircuit return to their initial or quiescent state.

This instant of time depends upon the inductance of the primary winding37 which is connected in series with the collector circuit of thetransistor T,. This primary winding 37 forms a transformer together withthe secondary winding 38 and an adjustable ferromagnetic core 39. Theferromagnetic core 39 is coupled to the membrane of a pressure-sensingdevice 41, by way of a mechanical linkage 40. The pressure-sensingdevice 41 is located directly behind the gas pedal 36, when viewed fromthe intake direction. The gas pedal 36 is coupled to the throttle valveor flap 50 within the intake manifold 12. When the absolute pressurewithin the the intake manifold 12 drops, the inductive coupling betweenthe primary and secondary windings is reduced through the withdrawal ofthe ferromagnetic core.

One terminal or end of the coil of the secondary winding 38, isconnected to the base of the transistor T,, through a diode 45. Theother end of this coil of the secondary winding 38 is connected to thejunction of two resistors 43 and 44 connected in series and across thepositive voltage supply line 26 and the negative voltage supply line 29.When the switching arm 32 is brought against the stationary contact ofthat switch through the cam 31, the transistor T, is turned off via adiode 42. As a result, the transistor T, can deliver current through theprimary winding 37. This current through the primary winding rises at arate which is inversely proportional to the inductance, and therebygives rise to an induced voltage within the secondary winding 38. Thisinduced voltage maintains the transistor T, in the conducting state andindependent of any further positioning of the switching arm 32. Thisconducting state of the transistor T is held until the current in theprimary winding 37 has substantially attained the saturated value. Theinduced voltage which maintains the transistor T, cut off by way of thediode 45, decreases as the saturation increases. This induced voltagethen finally drops to the extent that the negative base potential of thetransistor T, adjusted by the resistors 43 and 44, is exceeded. At thatpoint, the transistor T, is returned to its initial conducting state. Assoon as this initial state of the transistor T, is attained, the powertransistor 21 is cut off and the injection process or cycle isterminated.

With this electrical control system, the duration of the opening pulse23 depends upon the suction pressure prevailing within the intakemanifold 12, behind the throttle valve or flap 50, viewed from theintake direction. When, however, for purposes of acceleration, the gaspedal 36 is depressed and the throttle 50 is thereby turned to a greateropening angle as a result of the mechanical linkage of coupling rod 51,the suction pressure will tend to rise only with delay in contrast withthe opening motion of the throttle flap.

For the purpose of achieving an acceleration enrichment which takesplace immediately, in any event, a second adjustable throttle valve orflap 55 is provided behind the throttle 50 which is actuated by the gaspedal 36, viewed from the intake direction. This throttle 55 is set oradjusted as a result of the pressure difference between the intakemanifold and the atmospheric pressure of the surrounding air.

The second throttle flap 55 is rotatable through an angle ofsubstantially about a horizontal axis 56. The throttle flap isfunctionally connected with the membrane 61 of a pressure differencesensing device 62, by way of the linkage members 57, 58, 59 and rod 60.The pressure difference sensor 62 includes a first pressure chamber 63and a second chamber 64. A compression spring 65 which maintains themembrane 61 tensioned, is situated within the chamber 64. Through arelatively large bore or opening 66, the second pressure chamber 64communicates with that portion of the intake manifold 12, which isdirectly behind the second throttle member 55 within the intake manifold12. The pressure chamber 64 thereby also communicates directly with theindividual branches of the intake manifold.

The first pressure chamber 63 of the pressure-sensing device 62communicates with the section of the intake manifold 12, between thefirst throttle 50 and the second throttle 55. This communication betweenthe pressure chamber 63 and this section of the intake manifold, isachieved through a short communicating pipeline or tube 68. A connectingmember 69 connects, furthermore, this particular section of the intakemanifold between the two throttle valves, to the pressure-sensing device41, which operates upon the duration of the opening pulse in the mannerdescribed above. The communicating line or tubes 68 contains an orificeor throttle location 70 in the proximity of the intake manifold 12. Thisthrottle opening 70 has a relatively small cross-sectional opening whichaffects the opening time constant of the second throttle 55, in a mannerto be described.

In operation, the pressure difference applied to the membrane 61 isequivalent to the pressure drop at the second throttle 55. This pressuredrop balances the force of the spring 65 under steady state conditionsof operation corresponding to constant speed of the engine andnonvarying position of the second throttle member. For each operatingcondition of the internal combustion engine, the throttle flap or member55 assumes that position at which its pressure drop is a minimum. Thepressure drop cannot be made precisely zero, since use is made of theprinciple of a proportional regulator with a regulating deviationproportional to the positioning force. This pressure drop can, however,be held sufficiently small through a large effective surface of themembrane 63 and sufficiently large lever relationship within the linkageor lever members 57, 58 and 59.

Assume that while the engine is running, the gas pedal 36 is depressedrapidly from its idling position to operation under load, so that thethrottle 50 becomes rapidly opened. As a result, the air pressurebetween the two throttle members 50 and 55 rises practically withoutdelay, within the intake manifold. The pressure applied to thepressure-sensing device 41 thereby also rises without any substantialdelay. Such pressure rise taking place almost immediately, is due to thecondition that the second throttle member cannot immediately follow theopening motion of the first throttle. The pressure rise within the firstchamber 63 of the pressure difference sensing device 62 does not takeplace rapidly or in a steep manner. Instead, this pressure rise occursslower, the narrower the opening of the throttle position or orifice 70.However, the higher the pressure rising within the first chamber 63, thegreater is the amount by which the rod 60 is depressed downward. Suchdownward depression of the rod 60 moves the second throttle 55 in theopening direction. Such opening motion of the throttle flap 55 takesplace until there is a force balance between the pressure or forceapplied by the spring 65, and the pneumatic pressure drop at thethrottle 55 prevails.

in the disclosed embodiment of the present invention, the secondthrottle flap 55 is provided in the form of a rotatable member about theaxis 56. At the same time, it is also possible to provide, instead, adamper plate or air valve for this second throttle arrangement, and toset this air damper or air valve as a function of the pressuredifference.

In another embodiment of the present invention, shown in part in FIG. 3,possible to vary the cross-sectional area of the throttle location ororifice 70, as a function of the operating temperature of the engine.Such variation in the throttle position 70 may be made with the aid of,for example, a bimetallic spring 72 connected to a turntable valvemember 75 at the inlet orifice of the tube 68 so that the orificeopening is made smaller with decrease in operating temperature. Throughsuch design, the transient enrichment process for cold engines may beenlarged or increased in an advantageous manner.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied infew injection arrangements for internal combustion engines, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

What I claim as new and desire to be protected by Letters Patent is setforth in the appended claims.

1. A fuel injection arrangement for an internal combustion enginecomprising, in combination, at least one electromagnetically actuatedinjection valve; first throttle means within the intake manifold of saidengine and actuated by the gas pedal of said engine; second throttlemeans within said intake manifold and behind said first throttle withrespect to the intake direction of said intake manifold; means forcontrolling the position of said second throttle means as a function ofthe difference in pressures behind said first and second throttle means;pressure-sensing means communicating with said intake manifold betweensaid first and second throttle means; and control means actuatedsynchronously with the crankshaft rotation of the engine and operativelycoupled to said pressure-sensing means, said control means applyingpulses to said injection valve for opening said valve, the duration ofsaid pulses being dependent upon the pressure prevailing within saidintake manifold.

2. The fuel injection arrangement as defined in claim 1 wherein theopening time constant of said second throttle means is freelyselectable.

3. The fuel injection arrangement as defined in claim 1 wherein saidmeans for controlling said second throttle means comprises a pressuredifference sensing device having a first pressure chamber communicatingwith the intake manifold in front of said second throttle means andhaving a second pressure chamber communicating with the intake manifoldbehind said second throttle means with respect to the intake directionof said manifold.

4. The fuel injection arrangement as defined in claim 3 including atleast one connecting member between one of said chambers and said intakemanifold; and means cooperating with said connecting means for applyingsubstantial resistance to flow through said connecting means.

5. The fuel injection arrangement as defined in claim 4 wherein saidmeans for applying resistance to flow through said connecting meanscomprises a member with an adjustable opening, said opening beingdecreased with increase in the operating temperature of said engine.

6. The fuel injection arrangement as defined in claim 5 includingbimetallic spring means for adjusting the size of said opening as afunction of the operating temperature of said engine.

7. The fuel injection arrangement as defined in claim 1 wherein saidmeans for controlling said second throttle means comprisespressure-sensing means having a first chamber communicating with saidintake manifold between said first and second throttle means; a secondchamber separated from said first chamber and communicating with saidintake manifold behind said second throttle means with respect to theintake direction of said manifold; a membrane member separating saidfirst and second chambers; spring means within said second chamber andtensioning said membrane member; and linkage means connectingmechanically said second throttle means with said membrane member,whereby said second throttle means is positioned as a function of theposition of said membrane member.

8. The fuel injection arrangement as defined in claim 7 including pipemeans connecting said first chamber with said intake manifold betweensaid first and second throttle means; and orifice means within said pipemeans for restricting the flow through said pipe means.

9. The fuel injection arrangement as defined in claim 7 wherein saidspring means comprises a compression spring.

10. The fuel injection arrangement as defined in claim 1 includingmonostable multivibrator means in said control means; switch meansoperated by the crankshaft of said engine and actuating said monostablemultivibrator means; and transformer means operatively coupled to saidmonostable multivibrator means and to said pressure-sensing means, theinductance of said transformer means being varied as a function of thepressure sensed by said pressure-sensing means.

1. A fuel injection arrangement for an internal combustion enginecomprising, in combination, at least one electromagnetically actuatedinjection valve; first throttle means within the intake manifold of saidengine and actuated by the gas pedal of said engine; second throttlemeans within said intake manifold and behind said first throttle withrespect to the intake direction of said intake manifold; means forcontrolling the position of said second throttle means as a function ofthe difference in pressures behind said first and second throttle means;pressure-sensing means communicating with said intake manifold betweensaid first and second throttle means; and control means actuatedsynchronously with the crankshaft rotation of the engine and operativelycoupled to said pressure-sensing means, said control means applyingpulses to said injection valve for opening said valve, the duration ofsaid pulses being dependent upon the pressure prevailing within saidintake manifold.
 2. The fuel injection arrangement as defined in claim 1wherein the opening time constant of said second throttle means isfreely selectable.
 3. The fuel injection arrangement as defined in claim1 wherein said means for controlling said second throttle meanscomprises a pressure difference sensing device having a first pressurechamber communicating with the intake manifold in front of said secondthrottle means and having a second pressure chamber communicating withthe intake manifold behind said second throttle means with respect tothe intake direction of said manifold.
 4. The fuel injection arrangementas defined in claim 3 including at least one connecting member betweenone of said chambers and said intake manifold; and means cooperatingwith said connecting means for applying substantial resistance to flowthrough said connecting means.
 5. The fuel injection arrangement asdefined in claim 4 wherein said means for applying resistance to flowthrough said connecting means comprises a member with an adjustableopening, said opening being decreased with increase in the operatingtemperature of said engine.
 6. The fuel injection arrangement as definedin claim 5 including bimetallic spring means for adjusting the size ofsaid opening as a function of the operating temperature of said engine.7. The fuel injection arrangement as defined in claim 1 wherein saidmeans for controlling said second throttle means comprisespressure-sensing means having a first chamber communicating with saidintake manifold between said first and second throttle means; a secondchamber separated from said first chamber and communicating with saidintake manifold behind said second throttle means with respect to theintake direction of said manifold; a membrane member separating saidfirst and second chambers; spring means within said second chamber aNdtensioning said membrane member; and linkage means connectingmechanically said second throttle means with said membrane member,whereby said second throttle means is positioned as a function of theposition of said membrane member.
 8. The fuel injection arrangement asdefined in claim 7 including pipe means connecting said first chamberwith said intake manifold between said first and second throttle means;and orifice means within said pipe means for restricting the flowthrough said pipe means.
 9. The fuel injection arrangement as defined inclaim 7 wherein said spring means comprises a compression spring. 10.The fuel injection arrangement as defined in claim 1 includingmonostable multivibrator means in said control means; switch meansoperated by the crankshaft of said engine and actuating said monostablemultivibrator means; and transformer means operatively coupled to saidmonostable multivibrator means and to said pressure-sensing means, theinductance of said transformer means being varied as a function of thepressure sensed by said pressure-sensing means.